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I’ve again stumbled upon someone claiming that one Raw is as good if not better then bracketing when making a HDR image…
Thought I’d debunk this ones and for all.

This is the bracket I used in this example, it’s from -4 ev to +4 ev, 9 exposures.

Out of those 9 exposures I made this HDR in Photomatix Pro 4. There are virtually no clipping just some pixels directly in the sun.

This is the middle (0 ev) Raw file.

This is the HDR from a single Raw file, using the same settings as in the above, both the white and black end are clipped, there are lots of noise and loss of detail. The shadow areas that are without details are turning grey because of the tonemapping tries to compensate for black, it could be pulled down but that wouldn’t change the amount actual dynamic range, just make it harder to see.

And finally this is the middle exposure Raw file converted without ever going to HDR, but using every slider in my raw converter to pull out every last bit of information. There are clipping in both highlight and shadow and excessive amounts of noise, but to my surprise, the detail in the shadow area are greater then the single Raw HDR.

Still, the dynamic range in this is no where near what it is in the multiple exposure version. There are times when using one single Raw file is the way to go, for example if you have moving targets, but generally bracketing gives you a wider dynamic range with much less noise.

Canon Ixus 100is

A bit over a week ago I bought a small pocket camera, a “Canon Ixus 100 is”. I installed CHDK on it so I can write DNG raw files but is it any point to shoot raw files on a small camera like the Ixus. I thought I’d test it… This image is the exact same exposure, the Jpeg is directly from the camera, non-modified. The DNG raw file is white balanced on the snow and the settings in Adobe Camera Raw 4.6 was on “Auto”.

This is the full frame and histogram of the Jpeg version.From what I can see there’s nothing much to complain about, clipped highlights in the sky and something seems odd in the shadow end too, kind of truncated.

This is the full frame and histogram of the DNG raw file. The dynamic range are a bit better… The Shadows are clipped but the image looks brighter anyway…

Comparing the compression details, the left is DNG the right is Jpeg… The DNG is more noisy but slightly more detailed, the Jpeg is quite blurry…

More more compression details, the boxes are auto-contrasted. Right DNG, left Jpeg.

This is approximately how much bigger the DNG file is, The DNG is under the Jpeg above. They are both 4000 x 3000 pixels but there are more information in the DNG file…
There’s some strange distortion that makes it very hard to align them I should test if the DNG file or the Jpeg is, later.

The DNG file is almost 3 times as big as the Jpeg, considering that you have to write both Jpeg and DNG (not only the DNG) it’s effectively 4 times the size.
I think it’s worth it if you are gonna edit the files but for the everyday snapshot it’s hardly worth the extra space and time it takes to save… The resolution is big enough to hide some of the compression artifacts and blur.

The reason the DNG files has more data is because the Jpeg is distortion corrected. I noticed that the horizon in one of my photos was curved in the Raw file but not in the Jpeg. Let’s post more pictures shall we… =)

Above is the Raw with heavy barrel distortion and below is the corrected Jpeg.

This is the DNG Raw file with the distortion corrected in Photoshop lens correction tool. You can clearly see where the extra data is coming from…

And this is how it turned out after I gave it a round in Photoshop…
It’s a good camera for it’s size, I start liking it more and more, the more I use it… =)